The production of multi-filament feed yarns from polymeric fiber-formers such as polyesters and linear polypropylene, through the use of spin melt techniques, is well-known in the art. Such techniques have been refined over the years by various design and component changes, permitting increased post spinning draw down. Substantial improvements with respect to spinning speed itself, however, appear to be limited by process dependency upon the existence of an efficient damage-free filament-quenching or cooling step. In effect, fast moving soft extruded filaments must be given sufficient strength and flexibility to withstand the substantial amount of take up stress common to modern high speed spinning techniques and equipment.
In general, air-quenching is preferred for such high speed production because of the fragile nature of most spun filaments, however, it is very difficult to assure an acceptable degree of quench for all filaments within large, multi-rowed filament bundles.
By way of example, a large spinnerette using a jet of quenching air at room temperature and flowing at a speed of about 100-600 ft/minute perpendicularly across the extruded filament bundle normally causes the rows of extruded filaments closest to the air jet to be more quickly cooled than geometrically more distant rows. The net result is a tendency to over-quench close filaments with increased risk of filament breakage attributed to cohesive or brittle fracture, while distant filaments tend to remain under-quenched, with increased risk of ductile failure during high speed take up.
As production spinnerette units have become larger, and operate at rates in excess of 1500 M/m, the above problems become acute, such that filaments close to the air jet must be exposed to the maximum allowable quench while distant filaments must be given a minimally acceptable quench. In short, any inadvertent changes in air temperature, spinning speed, post spinning draw down velocity, or melt temperature is very likely to result in failure of a substantial number of filaments within the fiber bundle.
While some progress as been made in avoiding brittle fracture by increasing post spinning filament draw down of high denier spun polyester filaments, including branched polyesters (ref. U.S. Pat. No. 4,113,704), such teaching does not solve or even directly address itself to the abovenoted limits imposed due to inefficiency of the air quenching step.
It is an object of the present invention to increase efficiency and flexibility of air-quench-dependent spin melt compositions for spinning processes.
It is a further object of the instant invention to improve continuity and maximize high speed spinning strength of polyolefin-containing melts, and a still further object of the present invention to obtain high speed spinning of multicomponent polyolefin-containing spin melts for producing good quality low melting fiber webs suitable for producing nonwoven material.